MOTOROLA
3-2
SYSTEM RESOURCES
CPU16
REFERENCE MANUAL
Figure 3-1 CPU16 Register Model
3.2.1 Accumulators
The CPU16 has two 8-bit accumulators (A and B) and one 16-bit accumulator (E). In
addition, accumulators A and B can be concatenated into a second 16-bit “double” ac-
cumulator (D).
Accumulators A, B, and D are general-purpose registers used to hold operands and
results during mathematic and data manipulation operations.
Accumulator E can be used in the same way as accumulator D, and also extends
CPU16 capabilities. It allows more data to be held within the CPU16 during operations,
simplifies 32-bit arithmetic and digital signal processing, and provides a practical 16-
bit accumulator offset indexed addressing mode.
20
16 15
8 7
0 BIT POSITION
A
B
ACCUMULATORS A AND B
ACCUMULATOR D (A : B)
D
E
ACCUMULATOR E
XK
IX
INDEX REGISTER X
YK
IY
INDEX REGISTER Y
ZK
IZ
INDEX REGISTER Z
SK
SP
STACK POINTER
PK
PC
PROGRAM COUNTER
CCR
PK
CONDITION CODE REGISTER/
PC EXTENSION REGISTER
EK
XK
YK
ZK
ADDRESS EXTENSION REGISTER
SK
STACK EXTENSION REGISTER
HR
MAC MULTIPLIER REGISTER
IR
MAC MULTIPLICAND REGISTER
AM
AM
MAC ACCUMULATOR MSB [35:16]
MAC ACCUMULATOR LSB [15:0]
XMSK
YMSK
MAC XY MASK REGISTER
F
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For More Information On This Product,
Go to: www.freescale.com
n
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